Binding of driveshafts and axles in part time 4WD systems, also called "axle wind up"









© 1997-2011 H. Pietschmann

Use of traction in 2WD in a turn

You are in a 2WD, surface is dry, traction account is 200, torque is using up 140, once you go into the turn 20 units of lateral force per tire eat away from the 200, leaving only a safety margin of 20. (200 -140 -40). Traction of the front tires is only used up by the lateral force. The traction account of the front wheels shows 160 unused units. Only 4WD makes use of them


Suddenly you spot a patch of sand on the surface of the turn (maybe a truck lost some sand) traction value of sand on pavement is very low (sand acts like little ball bearings under your tires), maybe 70 per tire, making it 140 for the 2 powered tires. 140 minus 140 minus 40 and the traction account is overdrawn by 40 and you slide out of the turn. Sliding many times leads to roll overs when the tires hit resistance (crack at roads edge, curb etc.)and trip. Vehicles rarely ever roll "untripped". See why full time 4WD is safer.

| 4WD layouts | crawl ratio | 4WD components |

Need for more torque and traction management in a 2WD vs 4WD

The "pumpkins" in the picture above are the differentials.